Integrated circuits are made possible by processes which produce intricately patterned material layers on substrate surfaces. Producing patterned material on a substrate requires controlled methods for removal of exposed material. Chemical etching is used for a variety of purposes including transferring a pattern in a photoresist onto underlying layers, thinning layers or thinning lateral dimensions of features already present on the surface. Often it is desirable to have a “selective” etch process that etches one material faster than another on the substrate surface. Such etch processes are said to be selective to the first material relative to another material because they etch the first material at a significantly faster rate. Selective etch processes have been developed for a variety of materials.
Etch processes may be performed by contacting the substrate with liquid, gaseous, and/or plasma etchants. Etch processes that do not have liquid etchants in direct contact with the substrate are commonly referred to as “dry etch processes.” Dry etch processes are often desirable for selective etch processes that form delicate nano-scale patterns in a semiconductor substrate because of the precise control of an etch stop and low impact on patterned features. For example, dry etch processes can be stopped rapidly by evacuating the substrate processing region and/or purging it with an inert gas. In contrast, wet etch processes that leave residual liquid etchants on exposed substrate surfaces are prone to over-etching a target material.
Some selective dry-etch processes involve the exposure of a substrate to remote plasma by-products formed from one or more precursors. For example, remote plasma excitation of ammonia and nitrogen trifluoride enables silicon oxide to be selectively removed from a patterned substrate when the plasma effluents are flowed into the substrate processing region. There has been significant progress developing selective dry etch processes using remote plasma excitation of the etchants to selectively remove one dielectric material relative to another. More recently, selective dry etch techniques are being developed to selective remove metals and metal oxides using dry-etch processes. The present application describes advances in the use of selective dry etch techniques to selectively etch particular metals and metal oxides from a substrate surface relative to one or more other materials.